Find/Search performance in mongoDB

Question

I have worked a lot with sql like databases but when it comes to nosql dbs my knowledge is limited. Planning the design of my application I asked myself if there are differences when you want to find an entry in the database and the parameters used for identification.

For example: To avoid duplicates I want to check the database if the entry exists before using the insertOne command. Are there any differences whether I use the _id field or an attribute I defined myself in the query when it comes to efficiency and speed? I think that the collection will not hold more than 10.000 items.

Because I’m able to set the _id field when inserting a dataset manually this could impact the overall performance.

Mongodb is not any different from relational databases in this regard. If a field is indexed, searches/lookups by that field will be fast. — Sergio Tulentsev
– Sergio Tulentsev, Commented Nov 16, 2019 at 15:21

str · Accepted Answer · 2019-11-16 15:21:30Z

1

Like with SQL databases, you can add indexes on arbitrary fields in MongoDB. There should not be a noticable difference between reads based on the _id index or on your own.

To avoid duplicates I want to check the database if the entry exists before using the insertOne command.

You should have a look at the upsert parameter which handles exactly this usecase. It either updates or inserts a document (hence the name, up-sert). Refer the MongoDB Node.js driver documentation for details.

answered Nov 16, 2019 at 15:21

str

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2 Comments

FredFloete Over a year ago

Are there any differences when I dont use another index? Therefore I may have two options: a) Overwrite the _id with the value of the attribute I would use to compare otherwise or b) create an index on that attribute

str Over a year ago

Without an index, the DB must perform a collection scan (i.e. it looks through every single collection). So yes, there is certainly a difference.

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